Bafang Mid-drive M510 - 250 watt making clicking / clunking noise after 1,300 miles

[Trevor George]

Well we cured "the noise" some weeks ago, by just dismantling as much as we could, taking a look and reassembling and the noise went away for around 150 miles.
Then I loaned it to a friend and after a while the noise came back . . grrrrr
So more investigation required.

We now think we have found the source of the noise in my Bafang M510 motor, and it's because of a small fault in the design in this particular motor which I am using, in the way the chain-ring spider is secured onto the crank axle.
It's held in place with an unusual design of locknut which requires a special Bafang tool to remove it or to tighten it.

Gear-changes made under power with this mid-drive Bafang M510 are harsh, which is why it has already broken several teeth on my rear gear-cassette, simply because the software / firmware does not cut off power to the motor when gear changes are made, so each each time a gear change is made it sends a shock to that locknut against the face of the chain-ring spider, which very slightly moves the locknut and loosens it over a long period of riding.

The clicking is caused by the chain-ring spider moving very slightly on the axle, and the sound is amplified by the motor box itself, which is why it sounded as if it was coming from inside the motor

The locknut still looks tight - but is not - so it allows a very tiny movement of the chain-ring spider on the crank, which is causing that ticking noise two times for every revolution of the chain-ring wheel.
When we reassemble my motor (or any similar ones) next time, we will put some thread-locking fluid (Loctite) onto the threads of the locking ring in the hope that neither the spider or the locking-ring will become loose again.
Job done . . we hope

 

[saneagle]

Well we cured "the noise" some weeks ago, by just dismantling as much as we could, taking a look and reassembling and the noise went away for around 150 miles.
Then I loaned it to a friend and after a while the noise came back . . grrrrr
So more investigation required.

We now think we have found the source of the noise in my Bafang M510 motor, and it's because of a small fault in the design in this particular motor which I am using, in the way the chain-ring spider is secured onto the crank axle.
It's held in place with an unusual design of locknut which requires a special Bafang tool to remove it or to tighten it.

Gear-changes made under power with this mid-drive Bafang M510 are harsh, which is why it has already broken several teeth on my rear gear-cassette, simply because the software / firmware does not cut off power to the motor when gear changes are made, so each each time a gear change is made it sends a shock to that locknut against the face of the chain-ring spider, which very slightly moves the locknut and loosens it over a long period of riding.

The clicking is caused by the chain-ring spider moving very slightly on the axle, and the sound is amplified by the motor box itself, which is why it sounded as if it was coming from inside the motor

The locknut still looks tight - but is not - so it allows a very tiny movement of the chain-ring spider on the crank, which is causing that ticking noise two times for every revolution of the chain-ring wheel.
When we reassemble my motor (or any similar ones) next time, we will put some thread-locking fluid (Loctite) onto the threads of the locking ring in the hope that neither the spider or the locking-ring will become loose again.
Job done . . we hope

Did you try a gear sensor? They're pretty good at solving shifting issues, though the delay when shifting during a steep climb can be annoying.

 

[guerney]

The locknut still looks tight - but is not - so it allows a very tiny movement of the chain-ring spider on the crank, which is causing that ticking noise two times for every revolution of the chain-ring wheel.
When we reassemble my motor (or any similar ones) next time, we will put some thread-locking fluid (Loctite) onto the threads of the locking ring in the hope that neither the spider or the locking-ring will become loose again.
Job done . . we hope

It was due to a loose lockring once on my BBS01B converted bike, a creaking noise. Loose lockring which led to loose bolts. Same solution: Loctite, hasn't happened since.

Gear-changes made under power with this mid-drive Bafang M510 are harsh, which is why it has already broken several teeth on my rear gear-cassette, simply because the software / firmware does not cut off power to the motor when gear changes are made, so each each time a gear change is made it sends a shock to that locknut against the face of the chain-ring spider, which very slightly moves the locknut and loosens it over a long period of riding.

I don't know anything about the M510 - does your bike have a gear sensor? If not, can one be installed? Works great cutting off power to allow gear changes on my BBS01B, but others with the same kit on other bikes have reported it doesn't work as wonderfully on theirs, and I don't know why that is. The only time I have trouble with my gear changes is when it's pelting down with rain and I'm ascending a steep hill, when there is not quite enough cutoff time for the gear change. Unfortunately, there's no setting in the firmware to change that time interval.

If you do manage to install a gear sensor, it might be a good idea to cover both ends with self-amalgamating rubber tape to keep out moisture and dirt - I did that and it's still working great with no problems despite oodles of rain and dirt a couple of years on.

 

[Trevor George]

Did you try a gear sensor?

I would have loved to try a gear-change-sensor, but there is no way on my particular motor, or in the controller box, to plug one in.
I think it may be an early model, before it was improved.

 

[georgehenry]

A primitive but effective method of stopping lock rings coming undone on old British motorbikes was to use lock wire so it physically could not come undone.

 

[Trevor George]

A primitive but effective method of stopping lock rings coming undone on old British motorbikes was to use lock wire so it physically could not come undone.

Thanks . . but this particular locking ring is large diameter, and not much 'meat' to it, and not easy to access either, so I don't think it will be possible . . but thanks for the idea anyway

 

[guerney]

I would have loved to try a gear-change-sensor, but there is no way on my particular motor, or in the controller box, to plug one in.
I think it may be an early model, before it was improved.

Like I said, I don't know anything about the M510 - would this work? Or would it brick your controller? Might well be worth asking the company which gave you the bike.

https://www.aliexpress.com/i/1005004297494351.html

 

[saneagle]

I would have loved to try a gear-change-sensor, but there is no way on my particular motor, or in the controller box, to plug one in.
I think it may be an early model, before it was improved.

They plug into the brake connectors.

 

[Trevor George]

Like I said, I don't know anything about the M510 - would this work? Or would it brick your controller? Might well be worth asking the company which gave you the bike.

I already asked then that question, and also Bafang, and they said no available connectors in that particular motor

 

[Trevor George]

They plug into the brake connectors.

Haha . . it gets worse, as it doesn't have brake cutout switches, maybe because it was a prototype

 

[saneagle]

Haha . . it gets worse, as it doesn't have brake cutout switches, maybe because it was a prototype

That's weird. I never heard about that before. What about the cable that runs from the motor to the LCD? How many pins does it have at the motor end? Maybe you have a special cable that can be replaced.

 

[Trevor George]

That's weird. I never heard about that before. What about the cable that runs from the motor to the LCD? How many pins does it have at the motor end? Maybe you have a special cable that can be replaced.

Yep . . very weird indeed . . we have looked at all of the cables and plugs and nothing there to connect to
I think because the eBike was a prototype, and it was an early Bafang motor, they didn't consider those options.
At least the noise has gone, so I can enjoy riding again

 

[guerney]

Yep . . very weird indeed . . we have looked at all of the cables and plugs and nothing there to connect to
I think because the eBike was a prototype, and it was an early Bafang motor, they didn't consider those options.

I was hoping we'd see @saneagle help you identify the functions of the pins, and if possible, guide you through retrofitting brake cutouts and a gear sensor. I'm disappointed, but I expect I'll get over it.

 

[Trevor George]

I was hoping we'd see @saneagle help you identify the functions of the pins, and if possible, guide you through retrofitting brake cutouts and a gear sensor.

I really don't think it's possible on the beast which I have without extensive work, and maybe that early Bafang motor doesn't have the option, so I've learned to live with it, and just enjoy riding it within its limitations . . and at last . . No Noise from the motor

 

[saneagle]

I really don't think it's possible on the beast which I have without extensive work, and maybe that early Bafang motor doesn't have the option, so I've learned to live with it, and just enjoy riding it within its limitations . . and at last . . No Noise from the motor

...and broken gear teeth!

 

[Trevor George]

... and broken gear teeth!

<No Name> Rear Cassette replaced when it happened very early on with a stronger Shimano gear cassette, so no problems with broken teeth in the last 800 miles, thank goodness, despite the harsh gear changes which still happen under power, for example when climbing an incline when you don't wish to ease off and slow down to make the gear-changes

 

[SparkyB]

Hi when you took the motor apart did you have to replace the gasket? What did you use to open the motor up?

 

[Trevor George]

Hi when you took the motor apart did you have to replace the gasket? What did you use to open the motor up?

Hi . . I didn't need to replace the gasket, as I opened it carefully, and the gasket was fine I just carefully removed all of the bolts, and then used a screwdriver and hammer to gently separate the main cover, as shown in this video -

 

[SparkyB]

Hello again, can you advise on a lockring tool to remove the chainring it has 8 notches. Thanks

 

[saneagle]

Hello again, can you advise on a lockring tool to remove the chainring it has 8 notches. Thanks

You can use a hammer and screwdriver, hinged or fixed C-spabber or take a normal socket with the right diameter and use an angle grinder to grind the castellated shape - two or 4 lugs should be enough.

Or one of these:

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